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I. Gazic et al. / Tetrahedron: Asymmetry 16 (2005) 1175–1182
1181
4.6 mm ID, was performed by a slurry technique using a
Knauer pneumatic HPLC-pump. Solvents used for
HPLC chromatography were analytical grade from J.
T. Baker, and redistilled before use. The samples of ana-
lytes are prepared by dissolving ca. 1 mg of the racemic
compound in 1 mL of 2-propanol. For analytical pur-
poses 5 lL of freshly prepared solutions were used.
(1H, d, J = 7.9 Hz), 8.01–8.08 (3H, m), 8.42–8.53 (3H,
m), 8.91 (2H, s), 9.37 (1H, d, J = 6.7 Hz, N–H), 10.43
(1H, s, N–H). 13C NMR (DMSO-d6) d 17.61, 50.49,
114.33, 120.99, 121.40, 124.91, 124.94, 125.56, 125.80,
127.43, 127.62, 127.99, 128.51, 128.77, 130.42, 131.48,
131.65, 134.41, 135.81, 148.65, 161.72, 171.07.
4.3.1.6. (2S)-4-Chloro-N-[1-(3,5-dichloro-phenylcarba-
moyl)-ethyl]-3,5-dinitrobenzamide 13. Yield: 50%. 1H
NMR (DMSO-d6) d 1.39 (3H, d, J = 7.1 Hz), 4.50
(1H, dq, J = 7.1 and 7.0Hz), 7.23 (1H, t, J = 1.8 Hz),
7.62 (2H, d, J = 1.8 Hz), 8.81 (2H, s), 9.29 (1H, d,
J = 7.0Hz, N– H), 10.41 (1H, s, N–H). 13C NMR
(DMSO-d6) d 17.22, 50.59, 117.46, 121.50, 122.62,
127.42, 134.06, 134.26, 141.21, 148.68, 161.81, 171.38.
4.3. Chemistry
4.3.1. Preparation of chiral selectors 8–13. The chiral
selectors 8–13 were prepared under the general proce-
dure described previously.10 The structures of the pre-
pared compounds were confirmed by 1H and 13C
NMR spectra.
4.3.1.1. (2S)-2-Chloro-N-[1-(3,5-dimethyl-phenylcar-
bamoyl)-ethyl]-3,5-dinitrobenzamide 8. Yield: 53%. H
4.3.2. Preparation of chiral stationary phases CSPs
2–7. A suspension of each from the set of chiral selec-
tors 8–13 (1.00 mmol), silica gel (3.00 g; Nucleosil 100-5
NH2 or Separon SGX NH2, 5 lm) and diisopropyl-
amine (1.0mL) in tetrahydrofurane (15 mL) was stirred
overnight at ambient temperature. The modified silica
gel was collected on a G-4 filter, washed with tetra-
hydrofurane and methanol and dried at 70 ꢁC for 4 h.
Both used starting silica gels exhibited very similar sep-
aration characteristics. Since we wanted to compare the
new CSPs with the CSP 1 originally prepared from
Nucleosil silica gel,10 we herein report the analytical
data only for CSPs prepared from Nucleosil 100-5
NH2 (C 2.46, N 0.96%).
1
NMR (DMSO-d6) d 1.42 (3H, d, J = 7.1 Hz), 2.22
(6H, s), 4.64 (1H, dq, J = 7.1 and 6.9 Hz), 6.69 (1H, s),
7.23 (2H, s), 8.54 (1H, d, J = 2.6 Hz), 9.02 (1H, d,
J = 2.6 Hz), 9.21 (1H, d, J = 6.9 Hz, N–H), 10.02 (1H,
s, N–H). 13C NMR (DMSO-d6) d: 18.03, 21.11, 49.84,
117.24, 120.80, 125.03, 126.23, 128.69, 137.76, 138.74,
139.82, 145.91, 148.60, 162.81, 170.23.
4.3.1.2. (2S)-4-Chloro-3,5-dinitro-N-(1-phenylcarba-
moyl-ethyl)-benzamide 9. Yield: 68%. 1H NMR
(DMSO-d6) d 1.40(3H, d, J = 7.1 Hz), 4.58 (1H, dq,
J = 7.1 and 7.0Hz), 6.98 (1H, dt, J = 6.5 and 1.0Hz),
7.24 (2H, t, J = 7.5 Hz), 7.55 (2H, d, J = 8.5 Hz), 8.81
(2H, s), 9.24 (1H, d, J = 7.0Hz, N– H), 10.07 (1H, s,
N–H). 13C NMR (DMSO-d6) d 17.66, 50.35, 119.34,
121.41, 123.37, 127.46, 128.64, 134.44, 136.86, 148.67,
161.66, 170.65.
CSP 2. Prepared from 8, yield 3.235 g. Anal. found C
7.29, H 1.82 and N 2.03%. As calculated on % C 1.0 g
of CSP contain 0.22 mmol of bound selector.
CSP 3. Prepared from 9, yield 3.195 g. Anal. found C
6.31, H 1.62 and N 1.80%. As calculated on % C 1.0 g
of CSP contain 0.21 mmol of bound selector.
4.3.1.3.
(2S)-4-Chloro-N-[1-(naphthalen-1-ylcarba-
moyl)-ethyl]3,5-dinitrobenzamide 10. Yield: 64%. 1H
NMR (DMSO-d6) d 1.59 (3H, d, J = 7.0Hz), 4.82–
4.86 (1H, m), 7.48–7.61 (4H, m), 7.80(1H, d,
J = 8.0Hz), 7.95 (1H, d, J = 8.0Hz), 8.06 (1H, d,
J = 7.6 Hz), 8.93 (2H, s), 9.37 (1H, d, J = 7.0Hz, N–
H), 10.14 (1H, s, N–H). 13C NMR (DMSO-d6) d
17.83, 50.32, 121.47, 122.51, 122.91, 125.55, 125.82,
125.98, 126.11, 127.59, 128.12, 128.37, 133.29, 133.72,
134.57, 148.70, 161.95, 171.63.
CSP 4. Prepared from 10, yield 3.213 g. Anal. found C
7.32, H 1.85 and N 2.05%. As calculated on % C 1.0 g
of CSP contain 0.21 mmol of bound selector.
CSP 5. Prepared from 11, yield 3.241 g. Anal. found C
7.74, H 1.90and N 2.17%. As calculated on % C 1.0g
of CSP contain 0.22 mmol of bound selector.
CSP 6. Prepared from 12, yield 3.092 g. Anal. found C
9.66, H 1.89 and N 2.36%. As calculated on % C 1.0g
of CSP contain 0.25 mmol of bound selector.
CSP 7. Prepared from 13, yield 3.183 g. Anal. found C
7.93, H 1.94 and N 2.22%. As calculated on % C 1.0g
of CSP contain 0.22 mmol of bound selector.
4.3.1.4.
(2S)-4-Chloro-N-[1-(naphthalen-2-ylcarba-
moyl)-ethyl]-3,5-dinitrobenzamide 11. Yield: 69%. 1H
NMR (DMSO-d6) d 1.44 (3H, d, J = 7.1 Hz), 4.63
(1H, dq, J = 7.1 and 7.0Hz), 7.38 (1H, t, J = 8.4 Hz),
7.41 (1H, t, J = 7.8 Hz), 7.57 (1H, dd, J = 7.0
and 2.0Hz), 7.73–7.86 (3H, m), 8.23 (1H, s), 8.84 (2H,
s), 9.29 (1H, d, J = 7.0Hz, N– H), 10.31 (1H, s,
N–H). 13C NMR (DMSO-d6) d 17.59, 50.46, 115.55,
120.06, 121.39, 124.60, 126.36, 127.21, 127.39, 127.43,
128.28, 129.78, 133.29, 134.43, 136.40, 148.66, 161.72,
170.91.
4.3.3. (2S)-4-Butylamino-N-[1-(3,5-dimethyl-phenylcar-
bamoyl)-ethyl]-3,5-dinitrobenzamide
15. Suspension
of (2S)-4-chloro-N-[1-(3,5-dimethyl-phenylcarbamoyl)-
ethyl]-3,5-dinitrobenzamide10 14 (0.5 mmol; 0.210 g)
and n-butylamine (1.5 mmol, 0.15 mL, previously dried
overnight under the solid KOH) in anhydrous tetra-
hydrofurane (10mL) was stirred overnight at room tem-
perature. After evaporation and chromatography on
silica gel, using a mixture of solvents CH2Cl2–CH3OH
4.3.1.5.
(2S)-4-Chloro-N-[1-(anthracen-2-ylcarba-
(10:0.5) as eluent, 193 mg (85%) of 15 was isolated as
20
D
moyl)-ethyl]-3,5-dinitrobenzamide 12. Yield: 91%. 1H
NMR (DMSO-d6) d 1.53 (3H, d, J = 7.1 Hz), 4.73
(1H, dt, J = 7.1 and 6.7 Hz), 7.42–7.50(2H, m), 7.62
orange powder; mp 194.0–195.0 ꢁC; ½a ¼ þ113:0 (c
1 mg/mL, DMF). IR (KBr) m 3560.5, 3496.9, 3332.7,
2967.5, 2935.7, 1666.7, 1631.2, 1555.2, 1535.1, 1514.8,